Photoredox-catalyzed protecting-group-free C -glycosylation with glycosyl sulfinate via the Giese reaction.

C -Glycoside analogs of naturally occurring glycoconjugates are useful tools for chemical biology studies, but their synthesis usually requires protection of the hydroxyl groups of the glycosyl donors. Here we report protecting-group-free and photoredox-catalyzed C -glycosylation with glycosyl sulfinates and Michael acceptors via the Giese radical addition.